The effect of beta-adrenergic blockade after encoding on memory of an emotional event

RATIONALE: The efficacy of methadone for treating heroin dependence derives, in part, from suppression of opiate withdrawal and attenuation of the effects of heroin. OBJECTIVES: The purpose of this double-blind, within-subject, inpatient study was to determine whether larger doses of methadone, which are more effective in the treatment of opioid dependence, produce greater or longer-lasting blockade of the effects of heroin in addition to adequate withdrawal suppression. METHODS: Participants were maintained on 30, 60, and 120 mg methadone (ascending order) for approximately 3 weeks at each dose. During each maintenance period, heroin challenges were administered at 4, 28, and 52 h after the last methadone dose. Opioid agonist effects and opioid withdrawal symptoms were assessed prior to heroin challenge. Challenge sessions consisted of three doses of heroin (0, 10, and 20 mg/70 kg; ascending order) 45 min apart. RESULTS: All three methadone maintenance doses produced similar agonist effects. Participants tested 4 h after receiving 120 mg methadone showed complete suppression of withdrawal symptoms and full attenuation of the effects of heroin. Thirty and 60 mg methadone suppressed withdrawal for up to 52 h, but failed to block completely the effects of heroin. The effects of heroin increased slightly at longer post-methadone intervals. CONCLUSIONS: Heroin use may persist during methadone treatment because low to moderate doses of methadone suppress withdrawal, but fail to eliminate the effects of heroin. These results provide a mechanism for the clinical observation that higher methadone doses are more effective at reducing heroin use.     

When "enough" is not enough: new perspectives on optimal methadone maintenance dose

Some methadone maintenance treatment (MMT) programs prescribe inadequate daily methadone doses. Patients complain of withdrawal symptoms and continue illicit opioid use, yet practitioners are reluctant to increase doses above certain arbitrary thresholds. Serum methadone levels (SMLs) may guide practitioners dosing decisions, especially for those patients who have low SMLs despite higher methadone doses. Such variation is due in part to the complexities of methadone metabolism. The medication itself is a racemic (50:50) mixture of 2 enantiomers: an active "R" form and an essentially inactive "S" form. Methadone is metabolized primarily in the liver, by up to five cytochrome P450 isoforms, and individual differences in enzyme activity help explain wide ranges of active R-enantiomer concentrations in patients given identical doses of racemic methadone. Most clinical research studies have used methadone doses of less than 100 mg/day [d] and have not reported corresponding SMLs. New research suggests that doses ranging from 120 mg/d to more than 700 mg/d, with correspondingly higher SMLs, may be optimal for many patients. Each patient presents a unique clinical challenge, and there is no way of prescribing a single best methadone dose to achieve a specific blood level as a "gold standard" for all patients. Clinical signs and patient-reported symptoms of abstinence syndrome, and continuing illicit opioid use, are effective indicators of dose inadequacy. There does not appear to be a maximum daily dose limit when determining what is adequately "enough" methadone in MMT.     

Effects of buprenorphine and methadone in methadone-maintained subjects

Buprenorphine, a partial mu opioid agonist, is an experimental medication under development for the treatment of opioid dependence as an alternative to methadone maintenance. The present study examined the relationship between level of opioid physical dependence and response to buprenorphine administration as part of a program to develop procedures for transferring patients from methadone to buprenorphine treatment. This laboratory study characterized the agonist and antagonist effects of acute doses of buprenorphine and methadone in subjects maintained on either 30 (n=7) or 60 (n=6) mg/day oral methadone. Test doses of placebo [sl. and PO), methadone (15, 30, and 60 mg PO) and buprenorphine (2, 4, and 8 mg sl.) were administered to volunteers residing on a closed residential unit. Subjective, physiological, observer-rated, and cognitive/psychomotor measures were collected for 6.5 h after test doses. Test doses of methadone, but not buprenorphine, constricted pupils and produced dose-related increases on subjective report measures reflecting opioid agonist drug effects. Agonist effects of methadone were more prominent in the 30 mg than in the 60 mg methadone maintenance condition. Buprenorphine, but not methadone, precipitated opioid withdrawal signs and symptoms that were more prominent in the 60 mg than in the 30 mg methadone maintenance condition. These findings suggest that abrupt transition from methadone to buprenorphine may produce patient discomfort that is positively related to both methadone maintenance dose and buprenorphine transition dose.     

Cessation of methadone maintenance treatment using buprenorphine: transfer from methadone to buprenorphine and subsequent buprenorphine reductions

BACKGROUND: Buprenorphine is used in the treatment of opioid dependence. Due to its pharmacology, the transfer from methadone to buprenorphine may precipitate withdrawal symptoms. METHODS: Methadone maintained patients with clinical indicators of stability who were seeking withdrawal from methadone were recruited from three Australian states. Patients on methadone doses between 30 and 40 mg were randomised to transfer to buprenorphine by a fixed dose (transfer at 30 mg methadone) or by a variable dose induction (transfer when 'uncomfortable'). A third group of patients with methadone doses less than 30 mg were transferred to buprenorphine at their entry methadone dose. Fifty-one patients were inducted onto buprenorphine using the same dosing protocol with the first dose of 4 mg buprenorphine. Following stabilisation on buprenorphine, patients gradually reduced the buprenorphine dose to 0 mg. Withdrawal severity and drug use was monitored. RESULTS: There were no significant difference between the transfer at 30 mg and transfer when 'uncomfortable' dosing protocols in severity of withdrawal on transfer from methadone to buprenorphine. Those on doses less than 30 mg reported significantly less withdrawal discomfort at transfer. All but one patient stabilised on buprenorphine. Thirty-eight of the 51 patients inducted onto buprenorphine reached 0 mg. CONCLUSIONS: Transfer from methadone to buprenorphine can safely occur from doses of around 30 mg of methadone. Buprenorphine dose reductions were well tolerated. Thirty-one percent of patients were not using heroin or methadone at 1-month follow-up.     

Detoxification from methadone maintenance: double-blind comparison of two methods.

A well-rehabilitated group of 22 methadone maintenance patients were detoxified under ambulatory and double-blind conditions, over 42 days, either by decreasing the daily dose of methadone and supplementing it by propoxyphene napsylate (M--PN), or by decreasing the daily dose of methadone administered in two equal doses given 12 hours apart (M--M). All of 12 (100%) M--M and 5 of 10 (50%) M--PN subjects were able to temporarily withdraw from methadone maintenance, although two of the M--PN patients required maintenance with propoxyphene napsylate to cease methadone maintenance. In our experience both detoxification methods employed appear superior to the standard withdrawal technique of simply reducing the daily methadone maintenance dose in a step-wise fashion.     

Efficacy of buspirone in the treatment of opioid withdrawal

In an attempt to develop a new opiate detoxification approach, the authors assessed the efficacy of buspirone in the treatment of acute heroin withdrawal. Buspirone, a drug interacting with the serotonergic system, was selected because there is evidence that a decrease in serotonergic neurotransmission may be involved in opiate withdrawal symptoms. Twenty-nine hospitalized heroin addicts were randomized to 4 groups: (1) placebo; (2) methadone; (3) buspirone 30 mg daily; (4) buspirone 45 mg daily. The double-blind trial started in all patients with a 5-day methadone stabilization period ending with a 30-mg dose. This was followed from days 6 through 12 by placebo in group 1 and by a methadone taper in group 2. Because of its delayed action, buspirone was started on day 1 in groups 3 and 4 and was continued, after methadone discontinuation, through day 12. On day 13, drugs and placebo were discontinued and patients were observed through day 14. Withdrawal symptoms were assessed with the "Subjective Opiate Withdrawal Scale" (SOWS) and the "Objective Opiate Withdrawal Scale" (OOWS). The SOWS and OOWS scores were significantly higher in the placebo group than in the methadone, buspirone 30 mg, and buspirone 45 mg groups. There were no significant differences in SOWS or OOWS scores when the methadone group was compared with each of the two buspirone groups or when the two buspirone groups were compared with one another. In conclusion, buspirone, a nonopiate drug with no abuse potential, a safe side effect profile and no withdrawal symptoms, at doses of 30 and 45 mg, was as effective as a methadone taper in alleviating the withdrawal symptoms of heroin addicts stabilized for 5 days with, and then withdrawn from, methadone. The use of buspirone could be particularly helpful in outpatient settings where the duration of the methadone taper recommended for detoxification can be lengthy.     

Pharmacokinetic interaction of nelfinavir and methadone in intravenous drug users

The effect of nelfinavir 1250 mg twice daily (b.i.d.) on the pharmacokinetics of methadone was determined in 14 HIV-negative methadone users. DESIGN: The methadone dose (20-140 mg/day) was stabilized and fixed for at least 1 month before nelfinavir (1250 mg b.i.d. for 8 days) was added to the regimen. The concentrations of methadone enantiomers were measured before and during nelfinavir treatment, and the concentrations of nelfinavir and its active metabolite, AG1402, were measured during nelfinavir treatment. Adverse events and withdrawal/intoxication symptoms were monitored throughout the study. RESULTS: Nelfinavir reduced the area under the concentration-time curve of R-methadone, and S-methadone by 43% and 51%, respectively. Nelfinavir and AG1402 concentrations were within the normal range of historical data, and no subject experienced withdrawal symptoms during the study or required dose adjustment during or after the study. CONCLUSIONS: Although nelfinavir reduced the plasma concentrations of both R- and S-methadone, it seems to have no impact on the maintenance dose of methadone. A routine reduction of methadone dose is not recommended when coadministered with nelfinavir.     

Serum Methadone as an Aid in Managing Methadone Maintenance Patients

Serial serum methadone levels were obtained in two patients who were experiencing significant difficulties (including subjective and objective evidence of the opiate withdrawal syndrome) while on methadone maintenance. A precipitous drop in blood levels of methadone was recorded 2 to 6 hours after ingestion. It was during this same time period that withdrawal symptoms were most severe. When methadone was administered on a divided dosage regimen, there was a dramatic clinical improvement in both patients and a marked flattening of the curve of serum methadone levels. This pilot study suggests that the current practice of administering methadone as a single daily dose to all patients needs reconsideration; serial serum methadone levels may be helpful in determining which patients do better on a divided dosage regimen.     

Diazepam and methadone blood levels following concurrent administration of diazepam and methadone

Results of a previous study indicated that the opioid effects of methadone were enhanced by the concurrent administration of diazepam in methadone-maintained subjects. To determine whether a pharmacokinetic interaction might account for this methadone-diazepam interaction, the plasma levels of methadone, diazepam and diazepam metabolites were determined in blood samples collected during that study. Five adult male patients on methadone maintenance (50-60 mg/day) were administrated single doses of placebo, diazepam (20 and 40 mg), methadone (100%, 150% and 200% of the maintenance dose), and four diazepam-methadone dose combinations (20 and 40 mg diazepam in combination with 100% and 150% of the maintenance dose). The results showed that the concurrent administration of methadone and diazepam did not significantly change the time-course or areas under the plasma concentration-time curve of methadone, diazepam or N-desmethyl-diazepam compared to the levels following the administration of either drug alone. Thus, plasma drug level analysis does not indicate a pharmacokinetic interaction between diazepam and methadone.     

Sublingual buprenorphine/naloxone precipitated withdrawal in subjects maintained on 100mg of daily methadone

RATIONALE: Acute doses of buprenorphine can precipitate withdrawal in opioid dependent persons. The likelihood of this withdrawal increases as a function of the level of physical dependence. OBJECTIVES: To test the acute effects of sublingual buprenorphine/naloxone tablets in volunteers with a higher level of physical dependence. The goal was to identify a dose that would precipitate withdrawal (Phase 1), then determine if withdrawal could be attenuated by splitting this dose (Phase 2). METHODS: Residential laboratory study; subjects (N=16) maintained on 100mg per day of methadone. Phase 1: randomized, double blind, triple dummy, within subject study. Conditions were sublingual buprenorphine/naloxone (4/1, 8/2, 16/4, 32mg/8mg), intramuscular naloxone (0.2mg), oral methadone (100mg), or placebo. Medication conditions were randomized, but buprenorphine/naloxone doses were ascending within the randomization. Phase 2: Conditions were methadone, placebo, naloxone, 100% of the buprenorphine/naloxone dose that precipitated withdrawal in Phase 1 (full dose), and 50% of this dose administered twice in a session (split dose). Analyses covaried by trough methadone serum levels. RESULTS: Six subjects did not complete the study. Of the 10 who completed, 3 tolerated up to 32mg/8mg of buprenorphine/naloxone without evidence of precipitated withdrawal. For the seven completing both phases, split doses generally produced less precipitated withdrawal compared to full doses. CONCLUSIONS: There is considerable between subject variability in sensitivity to buprenorphine's antagonist effects. Low, repeated doses of buprenorphine/naloxone (e.g., 2mg/0.5mg) may be an effective mechanism for safely dosing this medication in persons with higher levels of physical dependence.     

The use of plasma levels to optimize methadone maintenance treatment

The question of the optimal methadone dose during maintenance therapy is controversial. For both philosophical and practical reasons, therapeutic drug monitoring has not been generally used. Some therapists prescribe low doses of methadone more for psychological than pharmacological reasons. This study examines, in 104 methadone patients, the relation between self-rating, observer-rating, urine tests, HIV-1 serostatus, daily methadone doses and plasma levels of methadone. No differences were found between HIV-1 infected and seronegative patients in these respects. The optimal methadone plasma level as judged by self- and observer-rating was more than 150 ng/ml. For oral methadone, the best results are obtained in patients receiving more than 90 mg daily. We found a significant relationship between methadone dose and plasma levels, also in patients who also used illicit drugs. We conclude that therapeutic drug monitoring should become routine in methadone treatment to achieve optimum results, especially in patients who complain of withdrawal symptoms and continue high-risk behaviour.     

Human methadone self-administration: effects of dose and ratio requirement

The effects of response requirement and small doses of methadone on human oral self-administration of methadone were examined. Three methadone maintenance patients stabilized at a dose of 80mg methadone per day were recruited as subjects. Completing a response requirement, fixed ratio (FR) of 32, 64 or 128 responses (FR32, FR64, FR128) on one button dispensed 10ml of drug solution. Completing the equivalent response requirement on a second concurrently available response button dispensed 10ml of vehicle. The opportunity to respond was unavailable until the drug or vehicle had been consumed. Each 10ml of drug solution contained methadone doses of 0.027, 0.054 or 0.108mg/ml. The frequency of deliveries was limited so that subjects could not ingest more than 54mg of methadone; the difference between the 80mg daily methadone dose and the methadone consumed in session was administered 30min post-session. At FR64 and FR128 the frequency of deliveries decreased, at the 0.054 and 0.027mg/ml doses, relative to the frequency of deliveries at FR32. The amount of methadone consumed increased with increases in methadone dose and decreased with increases in FR size. These results demonstrate the reinforcing effects of small unit doses of methadone. This procedure provides a sensitive baseline for examining effects of other pharmacological interventions on methadone ingestion in humans.     

Opioid effects and opioid withdrawal during a 24 h dosing interval in patients maintained on buprenorphine

In maintenance patients methadone has been shown to produce considerable changes in opioid effects and withdrawal over the dosing interval. As a partial agonist buprenorphine may be expected to produce smaller changes, but the nature and magnitude of these changes have only been described for single doses. In the present study opioid effects and withdrawal were described in patients maintained on buprenorphine. Twenty four opioid dependent subjects were administered 16 mg buprenorphine tablets sublingually for 10 days. On day 10 plasma samples were collected and physiological, subjective and observer-rated measures collected pre-dose and at 14 time points during the dosing interval. No significant respiratory depression was observed. Consistent with the partial agonist properties of buprenorphine, other physiological and subjective changes were also of small magnitude. However, even at a once daily dose of 16 mg some patients experienced significant opioid withdrawal that was maximal at the end of the dosing interval. Buprenorphine maintenance should be associated with a high level of safety and a low level of disruption caused by changing opioid effects over the dosing interval, but some patients may require high doses or other strategies to completely suppress withdrawal.     

Retention rate and illicit opioid use during methadone maintenance interventions: a meta-analysis

The efficacy of methadone maintenance in opioid addiction was assessed in terms of programme retention rate and reduction of illicit opioid use by means of a meta-analysis of randomised, controlled and double blind clinical trials. The results were compared with interventions using buprenorphine and levo-acetylmethadol (LAAM). Trials were identified from the PubMed database from 1966 to December 1999 using the major medical subject headings 'methadone' and 'randomised controlled trial'. Data for a total of 1944 opioid-dependent patients from 13 studies were analysed. Sixty-four percent of patients received methadone, administered either as fixed or adjusted doses. Thus, 890 patients received > or = 50 mg/day (high dose group) and 392 were given < 50 mg/day (low dose group). Of 662 controls, 131 received placebo, 350 buprenorphine (265 at doses > or = 8 mg/day and 85 at doses < 8 mg/day) and 181 LAAM. High doses of methadone were more effective than low doses in the reduction of illicit opioid use (odds ratio [OR] 1.72, 95% confidence interval [CI] 1.26--2.36). High doses of methadone were significantly more effective than low doses of buprenorphine (< 8 mg/day) for retention rates and illicit opioid use, but similar to high doses of buprenorphine (> or = 8 mg/day) for both parameters. Patients treated with LAAM had more risk of failure of retention than those receiving high doses of methadone (OR 1.92, 95% CI 1.32--2.78). It is proposed that in agonist-maintenance programmes, oral methadone at doses of 50 mg/day or higher is the drug of choice for opioid dependence.     

Availability of Reliable Serum Methadone Determination for Management of Symptomatic Patients

Methadone, when used in the appropriate dose, prevents opioid withdrawal during the 24-hour period following medication. However, the appropriate dose for a given patient may be difficult to determine due to variations in methadone metabolism which is affected by many factors. Early opioid withdrawal, requiring a higher dose of methadone, is often difficult to diagnose because many of the symptoms are also symptoms of other syndromes common in the methadone maintenance population. In this study, ten patients in stable methadone maintenance treatment reporting ≥ 4 Himmelsbach signs of abstinence were compared with ten patients reporting fewer symptoms. Until recently, accurate, precise, and affordable determination of serum methadoe level has not been readily available from commercial laboratories. This study has found that such measures are now available. Serum specimens from each subject were sent to three commercial laboratories for determination of serum methadone level. Results from the three laboratories were highly correlated. No statistical correlation was found between serum methadone level and number of Himmelsbach signs. Of the subjects reporting four or more symptoms, 40% had low serum methadone levels (< 150 ng/ml); 60% did not. Of the subjects reporting fewer than four symptoms, 90% had serum methadone levels ≥ 150 ng/ml. Subjects with ≥ 4 Himmelsbach signs had lower dose-adjusted serum methadone levels, the amount of methadone circulating per mg dose, (t = 1.54, p = .0702). Thus, for patients who report symptoms which could be attributable to opioid withdrawal, measurement of serum methadone level may help to differentiate complaints due to early abstinence from those due to other medical conditions.     

Effects of sublingually given naloxone in opioid-dependent human volunteers

To determine whether sublingual naloxone could precipitate withdrawal in opioid-dependent subjects, naloxone was administered in increasing doses (0-8 mg in four or six sessions conducted over 2 days) to six heroin abusers and three methadone (30 mg/day, p.o.) maintenance patients. Two or three sessions were conducted per day with 2- to 2.5-h intervals between same-day sessions. Naloxone precipitated withdrawal in two of six heroin abusers and in all three methadone subjects. Naloxone is sufficiently absorbed sublingually to precipitate abstinence in dependent subjects, but naloxone doses up to 1-2 mg can be administered sublingually to opioid abusers/addicts without precipitating withdrawal.     

Naltrexone shortened opioid detoxification with buprenorphine.

This double-blind, randomized, placebo-controlled clinical trial evaluated the impact on withdrawal symptoms of (i) combining naltrexone with a 4-day buprenorphine taper for short opioid detoxification (NB Group), compared to (ii) using a 4-day buprenorphine taper alone, followed by naltrexone on day 8 (PB Group). Sublingual buprenorphine was administered on days 1-4 (26 mg total). For the NB Group (n = 32) escalating doses of oral naltrexone were given on days 2-8 (placebo day 1). For the PB Group (n = 28) placebo was given on days 1-7 and naltrexone on day 8. Main outcome measures were Observed Opioid Withdrawal scores (OOW, 0-30) and use of medications to treat opioid withdrawal. Of 32 patients in the NB group, 59% experienced clinically relevant withdrawal (defined as OOW > or = 5) on day 2, but, after day 5, none experienced withdrawal. In the PB group, the number of patients experiencing withdrawal increased over time. The first naltrexone dose induced comparable withdrawal in both groups: peak OOW scores were (mean +/- SD) 5.2 +/- 3.3 on day 2 for the NB group, and 4.0 +/- 3.9 on day 8 for the PB group (NS), though, on day 2, 7 patients dropped out in the NB group and none in the PB group, while only one patient dropped out in the PB group on day 8. Throughout the 8-day study, patients in both groups received similar amount of adjunct medication: 0.64 +/- 0.07 mg (NB group) of clonidine vs 0.73 +/- 0.15 mg (PB group; NS). Only 25% of patients required use of sedatives (up to 20 mg diazepam). Starting naltrexone on day 2 appeared to abolish withdrawal symptoms after day 5 and, thus, to shorten the duration of withdrawal symptoms. Peak withdrawal symptoms after naltrexone were of moderate intensity, suggesting that naltrexone combined with buprenorphine is an acceptable and safe treatment for shortened opioid detoxification and induction of naltrexone maintenance.     

Combined use of trazodone-naltrexone versus clonidine-naltrexone in rapid withdrawal from methadone treatment. A comparative inpatient study

Trazodone is a non-tricyclic antidepressant drug with specific antagonistic activities at 5-HT(2) and alpha-1 adrenoceptors. We test the efficacy of trazodone (T) compared with clonidine (C) in rapid opiate detoxification (ROD) from methadone after reduction to a daily maintenance dose 相似文献